1. Field of the Invention
The present invention relates to an exhaust gas recirculation valve provided in an exhaust gas recirculation passage in an internal combustion engine such as a diesel engine or a gasoline engine.
2. Description of the Prior Art
FIG. 6 is a longitudinal sectional view showing the internal structure of a conventional exhaust gas recirculation valve. Referring to the figure, a valve housing 1 is disposed in connection with an exhaust gas recirculation passage (not shown) of an engine serving an internal combustion engine. The valve housing 1 has a concave portion 2 opened at the top end thereof, an exhaust gas inlet port 3 communicated with the engine exhaust system (not shown) in the lower portion of the bottom wall of the concave portion 2, an exhaust gas outlet 4 communicated with the engine air intake system (not shown), an exhaust gas passage 5 communicated with the exhaust gas inlet port 3 and exhaust gas outlet 4, and a part assembly opening 6 in the bottom portion thereof.
A valve seat 7 is press-fitted and set in the exhaust gas passage 5, a bushing 8 serving as a bearing is press-fitted and set halfway in the exhaust gas passage 5 within the valve housing 1, a valve rod 9 is slidably inserted in the bushing 8, a valve 10 is attached on the bottom end of the valve rod 9 and operable to move for closing and opening in an abutting and moving-away direction to the valve seat 7, a spring holder 11 is fixed on the top end of the valve rod 9 by caulking means, a coil spring 12 is installed between the spring holder 11 and the bottom wall of the concave portion 2, and the coil spring 12 becomes a pushing means to push the valve 10 in a valve-closing direction to abut on the valve seat 7.
A cooling water passage 13 is provided around the bottom wall of the concave portion 2 of the valve housing 1, and the cooling water passage 13 is operable to be connected with a cooling water inlet side pipe (not shown) and a cooling water outlet side pipe (not shown) for being communicated with a cooling water passage in the engine system. A holder portion 14 is integrally formed in the bottom wall portion of the concave portion 2 for preventing a deposit from entering the bushing 8 and a blocking member 15 blocks the part assembly opening 6.
A stepping motor 20 controls and drives the valve 10 in an opening and closing direction serving as a valve driving means, and a motor housing 21 houses the motor. The motor housing 21 has an opening portion on the bottom surface thereof, and a spacer 23 for water-proofing is previously clamped through a rubber seal ring 22 by a clamp screw 24 on the downward surface of the fringe in the opening portion. The motor housing 21 in which the seal ring 22 and spacer 23 are thus unitized is clamped through the spacer 23 by a mounting screw 25 on the top end portion of the valve housing 1.
Two yokes 26 for forming a magnetic path are assembled and fixed within the inner circumference surface of the motor housing 21, two coil bobbins 27 are incorporated within the yokes 26, solenoid coils 28 serving as a motor coil are wound around each coil bobbin 27, and the solenoid coils 28 are electrically connected with a terminal 29 serving as a connecter. The terminal 29 is electrically connected with the pulse-sending portion of a control unit (not shown).
A rotor 30 is rotatably held by bearings 31 and 32 inside the motor housing 21, the bearing 31 existing on the top side of the rotor 30 is incorporated in the motor housing 21, and the bearing 32 existing on the bottom side of the rotor 30 is incorporated in the spacer 23. A magnet 33 is held on the outer circumference of the rotor 30, and a motor shaft 34 is configured to threadedly penetrate the center of the rotor 30. The motor shaft 34 is located on the extended axis of the valve rod 9.
A motor bushing 36 is fit in the central opening of the spacer 23, and the motor shaft 34 is fit slidably in the motor bushing 36. A motor spring holder 37 is coupled with the bottom end portion of the motor shaft 34 and lies under motor bushing 36. A motor coil spring 38 lies between the motor spring holder 37 and spacer 23. The motor coil spring 38 becomes a pushing means of pushing the motor shaft 34 in the opening direction of the valve 10.
The operation in the conventional exhaust gas recirculation valve will next be described.
First of all, when the valve 10 is opened from the fully closing state, the solenoid coil 28 of the stepping motor 20 is excited by a pulsed voltage fed from the control unit (not shown) to the terminal 29. The rotor 30 including the magnet 33 thereby stepwise rotates in the direction of valve opening. At this stage, precise open-loop control is performed because the number of the sent pulse is coincident with the step number. This stepwise rotation is changed to a rectilinear motion by a screw feed action through the threaded engagement between the rotor 30 and motor shaft 34, and thereby the motor shaft 34 travels in the direction of valve opening. At this stage, the travel of the motor shaft 34 is assisted by the pushing force of coil spring 38. At the moment when the top end of the valve rod 9 abuts on the bottom end of the motor shaft 34 by such travel of the motor shaft 34, the valve rod 9 moves down by the driving force of the motor shaft 34 against the upward pushing force of the coil spring 12, and at the same time the valve 10 provided on the bottom end of the valve rod 9 also moves down toward the valve seat 7, to thereby open the valve. Thereby, the exhaust gas inlet port 3 and exhaust gas outlet 4 are communicated with each other through the exhaust gas passage 5.
When the valve 10 is closed, the above operation is reversed. That is, the rotor 30 containing the magnet 33 stepwise rotates in the direction of closing the valve by the pulsed voltage sent from the control unit to the terminal 29, and thereby the motor shaft 34 moves up in the direction of the closing valve. Following the movements, the valve rod 9 also moves up assisted by the upward pushing force of the coil spring 12, and thereby the valve 10 closes the opening of the valve seat 7.
Since the conventional exhaust gas recirculation valve is constructed as mentioned above, there exists the following drawbacks. Since the cooling water is introduced into the cooling water passage 13, the cooling of the system of the valve 10 containing the stepping motor 20 and valve housing 1, that is, the cooling of so-called valve body can be performed by use of the cooling water. However, because the cooling water passage 13 is provided around the valve housing 1, the size of the valve body should be large, and further piping for connecting the cooling water passage 13 to the cooling water passage of the engine system is required. Thus, this requires a dedicated water-cooling piping for the exhausted gas recirculation valve in which the number of components is large and the construction thereof is complicated, which results in high-cost.
The present invention has been accomplished to solve the above-mentioned drawback. An object of the invention is to provide an exhaust gas recirculation valve which may prevent the valve and valve-driving means in the exhaust gas recirculation system from being overheated at an elevated temperature, thereby resulting in cost-down, without a dedicated water-cooling piping for the exhaust gas recirculation valve.
Another object of the invention is to provide an exhaust gas recirculation valve in which the cooling water of the engine system can directly cool the valve housing of the exhaust gas recirculation system with efficiency.
Still another object of the invention is to provide an exhaust gas recirculation valve in which the taking-out passage of cooling water from the engine system can be easily provided within the valve housing itself.
A further object of the invention is to provide an exhaust gas recirculation valve operable not to make the pool of the cooling water within the portion of the valve housing on which the cooling water from the engine system is directly applied, and operable to thereby obtain the high circulation performance of the cooling water.
An exhaust gas recirculation valve according to the present invention comprises: a valve housing disposed in connection with an engine block having the cooling water passage of an engine system and the exhaust gas recirculation passage thereof; an exhaust gas passage formed in the interior of the valve housing and connected with the exhaust gas recirculation passage; a valve opening and closing the exhaust gas passage; and a valve-driving means driving and controlling the valve in an opening and closing direction, wherein in the wall portion of the valve housing, a cooling-water-taking-out passage having a cooling water inlet port opened in the to-be-connected surface of the valve housing to the engine block and taking out the cooling water from the cooling water passage of the engine block is integrally formed, and the cooling water inlet port of the cooling-water-taking-out passage is configured to be connected with the cooling water passage by connecting the valve housing to the engine block.
An exhaust gas recirculation valve according to the present invention comprises: a valve housing disposed in connection with an engine block having the cooling water passage of an engine system and the exhaust gas recirculation passage thereof; an exhaust gas passage formed in the interior of the valve housing and connected with the exhaust gas recirculation passage; a valve opening and closing the exhaust gas passage; and a valve-driving means driving and controlling the valve in an opening and closing direction, wherein a water outlet in which a cooling-water-taking-out passage for taking out the cooling water from the cooling water passage of the engine block is formed is integrally incorporated between the engine block and the valve housing.
The cooling-water-taking-out passage within the water outlet of an exhaust gas recirculation valve according to the present invention has an intermediate opening portion provided at a halfway position therein and operable to apply the cooling water coming from the cooling water passage of the engine block directly over the wall surface of the valve housing.
The intermediate opening portion of the cooling-water-taking-out passage of an exhaust gas recirculation valve according to the present invention is formed by partially removing the wall portion of the water outlet on the side where the outlet is connected with the valve housing.
The intermediate opening portion of the cooling-water-taking-out passage of an exhaust gas recirculation valve according to the present invention has a channel construction operable not to make the pool of the cooling water between the intermediate opening portion and the wall portion of the valve housing.